Chapter 9: Nervous Tissue

Question 1

What are the functions of the nervous system?

Answer 1

• Sensory
  
  • • senses changes within the body and environment
• Motor
  
  • • initiates muscle movements or glandular secretion
• Integrative
  
  • • interprets sensory info and decides the appropriate motor response.

Question 2

What is the function of the afferent neurons?

Answer 2

Conducts impulses from sensory cells to central nervous system (CNS).

Question 3

What are the 2 subdivisions of the autonomic nervous system?

Answer 3

1. Sympathetic

2. Parasympathetic

Question 4

What is the function of microglia?

Answer 4

Acts as phagocytotic cells.

Question 5

What are ependymal cells?

Answer 5

Epithelial cells (often ciliated) that line the ventricles of the brain.

Question 6

What do ependymal cells produce?

Answer 6

Cerebrospinal Fluid (CSF)

Question 7

Describe the structure of a myelin sheath.

Answer 7

Consists of many layers of phospholipid membrane that belongs to schwann cells.
–the sheath wraps around axons on the myelinated neurons.

Question 8

What are dendrites?

Answer 8

Extensions of the cell body that transmit impulses to the cell body.

Question 9

White Matter

Answer 9

Groupings of myelinated processes of many neurons

Question 10

What does Grey Matter contain?

Answer 10

Contains nerve cell bodies, dendrites, and axon terminals of unmyelinated axons and neuroglia.

Question 11

Ganglia

Answer 11

Clusters of nerve cell bodies outside the CNS.

Question 12

Resting Potential

Answer 12

The potential difference that exists across a nerve cell membrane when it is not conducting an impulse
– usually about -70 millivolts.

Question 13

What is the role of the sodium-potassium pump?

Answer 13

Actively carries sodium out of the cell and potassium into the cell.

Question 14

What is the sodium-potassium pump powered by?

Answer 14

ATP

Question 15

How does a neuron become depolarized?

Answer 15

The rapid influx of sodium ions through the nerve cell membrane causes depolarization.

Question 16

Refractory Period

Answer 16

The period of time following an initial stimulus, during which a neuron cannot be stimulated to conduct a second impulse.

Question 17

What is a threshold stimulus?

Answer 17

A stimulus that causes the membrane of a neuron to depolarize to a critical level (-55 mV) to generate an action potential?

Question 18

What is the advantage of saltatory conduction?

Answer 18

Its very fast and required less energy expenditure of the sodium-potassium pump.

Question 19

Why does the synaptic conduction of an impulse occur only in one direction?

Answer 19

Transmission must be unidirectional

• because neurotransmitters are released only from presynaptic terminals, and
• because only postsynaptic membranes have appropriate neurotransmitter receptors.

Question 20

Neurotransmitter

Answer 20

A chemical released by a presynaptic neuron for the purpose of stimulating or inhibiting the postsynaptic neuron.

Question 21

What type of nervous system is the sympathetic nervous system part of?

Answer 21

Autonomic Nervous System (ANS)

Question 22

What neuroglia produces myelin in CNS?

Answer 22

Oligodenfrocyte

Question 23

What gated ion channel opens to a change in membrane potential?

Answer 23

Mechanical Pressure

Question 24

What are the most important factors that determine the speed of impulse propagation??

Answer 24

• Fiber diameter

- Presence or absence of myelin sheath

Question 25

What doe the peripheral nervous system (PNS) consist of?

Answer 25

- Cranial and spinal nerves with sensory (afferent) and motor (efferent) components - Ganglia - Sensory receptors

Question 26

What does the somatic nervous system (SNS) consist of?

Answer 26

- Neurons that conduct impulses from cutaneous and special sense receptors to CNS - Motor neurons that conduct impulses from CNS to skeletal muscle tissue.

Question 27

What does the autonomic nervous system (ANS) consist of?

Answer 27

- Sensory Neurons from visceral organs. | - Motor neurons that convey impulses from CNS to smooth muscle tissue, cardiac muscle tissue, and glands.

Question 28

What does the enteric nervous system (ENS) consist of?

Answer 28

Neurons in the enteric plexuses that extend the length of gastrointestinal (GI) tract.

Question 29

What are subdivisions of PNS?

Answer 29

1. Somatic (voluntary) 2. Autonomic (involuntary) 3. Enteric nervous systems

Question 30

What is the function of a dendrite?

Answer 30

Conducts impulses from receptors or other neurons to cell body.

Question 31

What is the function of a axon?

Answer 31

Conducts nerve impulses: - from neuron to dendrite - to cell body of another neuron - to an effector organ of the body.

Question 32

What are the different types of neuroglia and their functions?

Answer 32

1. Astrocyte = blood brain barrier 2. Oligondendrocyte = support 3. Microglia = phagocytosic 4. Ependymal Cells = cerebrospinal fluid production 5. Schwann Cells = myelin production 6. Satellite cells = support

Question 33

What do voltage-gated ion channels respond to?

Answer 33

A direct change in membrane potential.

Question 34

What does ligand-gated ion channels respond to?

Answer 34

A specific chemical stimulus

Question 35

What do mechanically-gated ion channels respond to?

Answer 35

Mechanical vibration or pressure

Question 36

What is the typical value for the resting membrane potential?

Answer 36

- 70 mV | - ---meaning its polarized

Question 37

Action Potential (AP)

Answer 37

A sequence of rapidly occurring events that decrease and eventually reverse the membrane potential (depolarize).

Question 38

What can an action potential also be called?

Answer 38

An impluse

Question 39

What happens during the refractory period?

Answer 39

- Another impulse cannot be generated (absolute refractory period) OR - Can be triggered only by a suprathreshold stimulus (relative refractory period)

Question 40

What do Action Potential do?

Answer 40

Conducts or propagates (travels) from point to point along the membrane.

Question 41

Nerve impulse

Answer 41

Traveling action potentials

Question 42

How are neurotransmitters removed from the synaptic cleft?

Answer 42

1. Diffusion 2. Enzymatic Degradation 3. Uptake into cells (neurons and glia)